I have finally found the original author of the Java 5 grammar for SableCC that I posted here. I contacted author and the file has now been updated with appropriate author and license information.
Adding GPL or LGPL license information to a distribution is quite forward. There is a very straight forward howto: here at gnu.org.
Also I have added license information for my accompanying prettyprinter class. Both are available for download as tar-balls,
here and here.